/*
 * Copyright (C) 2008 Timothy D. Morgan
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 3 of the License.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
 *
 * $Id: lru_cache.h 122 2008-08-09 20:24:01Z tim $
 */

#ifndef LRU_CACHE_H
#define LRU_CACHE_H

#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

struct lru_cache_element;
typedef struct lru_cache_element lru_cache_element; 

struct lru_cache_element
{
  void* index;
  uint32_t index_len;
  void* data;
  lru_cache_element* next;
  lru_cache_element* older;
  lru_cache_element* newer;
};

typedef struct _lru_cache
{
  uint32_t secret;
  uint32_t num_keys;
  uint32_t num_buckets;
  uint32_t max_keys;
  lru_cache_element* oldest;
  lru_cache_element* newest;
  lru_cache_element** table;
  bool free_data;
} lru_cache;


lru_cache* lru_cache_create(uint32_t max_keys, uint32_t secret, bool free_data);
void lru_cache_destroy(lru_cache* ht);

/* Returns a pointer to the old, replaced data stored at index.  
 * Returns NULL if no entry was overwritten.
 */
bool lru_cache_update(lru_cache* ht, const void* index, 
		      uint32_t index_len, void* data);

/* Returns pointer to data previously stored at index.
 * If no data was found at index, NULL is returned.
 */
void* lru_cache_find(lru_cache* ht, const void* index, 
		     uint32_t index_len);

/* Removes entry from table at index.
 * Returns pointer to data that was there previously.  
 * Returns NULL if no entry is at index.
 */
bool lru_cache_remove(lru_cache* ht, const void* index, 
		      uint32_t index_len);

#endif
